Erik Mandaville Posted January 28, 2007 Share Posted January 28, 2007 For information. The attached link is related to the review of Welborne Labs DRD 300B monoblocks. It mentions Klipsch speakers, so I thought some might be interested. It also overtly states factors related to impedance compensation, which agree with my own experiences with certain kinds/orders of crossover network. IOWs, that an amplifier sees a relatively flat and even load impedance may look nice on paper, but the subsequent sound quality is probably subjective. We have owners of DRDs on this forum, and just thought I would include the following review: http://www.enjoythemusic.com/magazine/equipment/0206/welborne_laboratories_300b.htm Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 28, 2007 Author Share Posted January 28, 2007 Note, too, the discussion re: solid state vs hollow state rectification. If someone dismisses a design out-of-hand based simply on the type of rectifier the component uses......that's too bad. There are tube amps (OTL and more conventional) with stellar performance that use solid state derived DC in both HT and filament supplies. Erik Quote Link to comment Share on other sites More sharing options...
Deang Posted January 28, 2007 Share Posted January 28, 2007 In summation: If you add impedance compensation circuitry, "...it can cause the SET some real problems. These problems manifest themselves as veiling, flabby bass, midrange bloat or any number of other sonic irregularities. If you don't, and "these spikes reach much above (say) 50 ohms, then "this can spell disaster for an SET". So one way SET has "real problems", and the other way spells "disaster". I think the reviewer blew his foot off. He's overstating things a bit I think. Reactive filters will create some anomolies in response (non-flat), but I hardly think it spells disaster. I do agree with him that loading up the filter with all kinds compensation will "suck the life" out of the sound, but if you keep it simple and just use a swamping resistor you can have your cake and eat it too. The stock networks for the Klipschorn, LaScala and Belle Klipsch don't go much above 35 ohms, and I would think those would be just fine. The Cornwall, Heresy, Chorus, Forte, etc. might present some problems. Quote Link to comment Share on other sites More sharing options...
Parrot Posted January 28, 2007 Share Posted January 28, 2007 And since SET amps can get very loud, make sure to use hearing protection. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 28, 2007 Author Share Posted January 28, 2007 "I think the reviewer blew his foot off." Okay, that's fine. My impression was that he was simply describing aspects of speaker and crossover design that can be problematic for the type of amp in question. I've built higher order networks for different speakers, including our Klipschorns. With low power amps like the 1.5 watt SE OTL from Transcendent Sound or the 45, 2A3, or 300B amps I've made, I've found the fewer the coils the (much) better. If the reviewer's use of the word 'disaster' is synonymous with my thought that the higher order networks didn't and don't sound nearly as open (transparent?) and 'alive' as a simple type 'A,' I am in agreement with his premise. I would argue, though, that there may be some who might prefer the sound of more complex designs regardless of the type of amp being used. Let's see, where the flavor is like a nice cut of beef for one person, another might think it........tastes like chicken! I think passive networks in general are a sort of 'necessary' compromise, and that the best crossover would be none at all, which is what I think the reviewer was suggesting in terms of his Lowther horns. I also own those, and know what he's talking about. In that our options for multi-driver designs are either line-level/active crossing over or cumbersome, heavy coils of wire and bunches of caps (which can look kind of cool, I guess), my choice for the passive species would be for the fewer hunks of big wire. I tend to think the fellow is most likely still putting on two shoes in the morning. Erik Quote Link to comment Share on other sites More sharing options...
seti Posted January 28, 2007 Share Posted January 28, 2007 Interesting read thanks for posting. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 28, 2007 Author Share Posted January 28, 2007 small correction: 300Bs came after I used the higher order networks for parts I used to make a single coil, single cap network for my two-way monitors (which used to be a high order series design -- and really was disasterous with the kind of amp we've been talking about). Paul: LOL! another brilliant response. Chalk that one up! Quote Link to comment Share on other sites More sharing options...
seti Posted January 28, 2007 Share Posted January 28, 2007 small correction: 300Bs came after I used the higher order networks for parts I used to make a single coil, single cap network for my two-way monitors (which used to be a high order series design -- and really was disasterous with the kind of amp we've been talking about). Paul: LOL! another brilliant response. Chalk that one up! Just dripping with sarcasm imagine that....... Which 300Bs have you used? Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted January 28, 2007 Share Posted January 28, 2007 ..."The stock networks for the Klipschorn, LaScala and Belle Klipsch don't go much above 35 ohms, and I would think those would be just fine. The Cornwall, Heresy, Chorus, Forte, etc. might present some problems." So I'm assuming the stock crossovers on my Reference RB-75s may also fall into the "problem" category for this particular 300B DRD amp, or possibly for any/all SET amps...or am I mistaken? Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 28, 2007 Author Share Posted January 28, 2007 Jim: That reviewer was providing his own opinion of the situation based on what he heard. Just depends on what you like. If your RB-75s sound good to you, than the combination is fine. Erik Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 28, 2007 Share Posted January 28, 2007 Dean, "The stock networks for the Klipschorn, LaScala and Belle Klipsch don'tgo much above 35 ohms, and I would think those would be just fine." With an amp with high output impedance (most zero feedback SET) you will see large FR changes if the speaker has that wide of an impedance range. You can calculate it out if you know the output impedance of the amplifier. For example take a look here: http://www.stereophile.com/integratedamps/398/index4.html Look at the first two pictures. Notice how the *electrical* FR of the amp/speaker varies and that it tracks the impedance swings of the amplifier. If the speaker was *perfectly* flat acoustically (when driven by an amp with very low output impedance) the speaker would now be +1, -3dB just from the electrical interaction between amp and speaker. Shawn Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 29, 2007 Author Share Posted January 29, 2007 Shawn: Thanks for including the Stereophile link. Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 30, 2007 Author Share Posted January 30, 2007 "but if you keep it simple and just use a swamping resistor you can have your cake and eat it too." It's something I've tried many times. Each time I end up taking the resistor out. In short: Done that and don't like it. Seti: I'm using the 300Bs Jim T. gave me. Quote Link to comment Share on other sites More sharing options...
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